Potassium Fertilization in Onions in India

Evaluating Potassium Fertilization Strategy for Onion

Despite established fertilizer recommendations for nitrogen (N) and phosphorus (P), potassium (K) has received comparatively little attention in onion production (Kumara, Mansur et al. 2018). This study evaluated the effect of muriate of potash (MOP; KCl) on onion yield and profitability across 35 field trials conducted during the rabi seasons of 2018-19 and 2019-20 in western and central Maharashtra. Each site comprised paired plots with identical management differing only in the inclusion of MOP.

KCl Increases Onion Yield

The application of muriate of potash (MOP) significantly increased onion yield across all the sites, with an average absolute gain of 423 kg ha⁻¹ (13.7% relative increase). Profitability analysis indicated a strong economic return, with an average benefit-to-cost ratio of 5.0. Variation between years and drainage classes reflected the influence of soil-water dynamics on baseline yield levels and the yield gap available for potassium response. In 2018-19 (hot and dry conditions), imperfectly drained soils retained more moisture and achieved higher control yields, leaving a smaller yield gap and a weaker response to muriate of potash (MOP). In contrast, during 2019-20 (cooler and wetter conditions), baseline yields declined, particularly in imperfectly drained soils, resulting in larger yield increases and a stronger muriate of potash (MOP) response. District-level effects were not significant, indicating that local soil and moisture conditions, rather than geography, governed MOP performance.

Overall, the results confirmed that potassium as a limiting nutrient in many onion-growing soils of Maharashtra and demonstrated that MOP application can improve both productivity and profitability when adapted to local moisture conditions.

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